This project is a continuing investigation of the effects of interactions between epithelium and stroma during the transformation of epithelium from normal to neoplastic state. The systems currently being studied are: 1) Tumors of the submandibular salivary gland of mice, induced by polyoma virus; 2) Tumors of the forestomach and glandular stomach of mice, induced by chemical carcinogens; 3) Mammary tumors of mice, spontaneous or induced by mammary tumor virus (MTV). The general methods used involve neoplastic transformation of epithelium in the presence or absence of specific types of mesenchyme (stroma). The results are evaluated on the basis of morphological and biological properties of the resulting neoplasms. BIBLIOGRAPHIC REFERENCES: Dawe, C.J., Morgan, W.D., Williams, J.E., and Summerour, J.P.: Inductive epithelio-mesenchymal interaction: Is it involved in the development of epithelial neoplasms? In Muller-Berat, N. (Ed.): Progress in Differentiation Research. New York, Amer. Elsevier Pub. Co., Inc., 1976, pp. 305-318. Sakakura, T., Nishizuka, Y., and Dawe, C.J.: Mesenchyme-dependent morphogenesis and epithelium-specific differentiation in mammary gland. Science 194: 1439-1441, 1976.